The publications and other materials used herein to illuminate the background of the invention, and in particular, cases to provide additional details respecting the practice, are incorporated by reference.
In existing devices and methods for assessing the visual field of the eye there are several problems which affects the reliability of the results or makes the testing situation difficult for the person to be tested. In visual field testing it is essential that the orientation of the eye, i.e. where the line of sight (visual axis) or the fovea centralis of the retina of the eye is aimed at, or fixates, is accurately known. Only after this precise information one can present a stimulus in an accurate location in the visual field of a person.
In existing devices and methods the subject is asked to concentrate on a given, static fixation point and report on the presence and position of stimuli presented to their peripheral vision. This prolonged attempt of fixation on a given point is very unnatural and often uncomfortable eye behaviour for a person. Additionally the ability of the subject to accurately fixate is known to be poor especially over an extended period and so the accuracy of the visual field measurement is compromised.
In existing devices and methods the monitoring of the accuracy of the fixation of the eye is usually done with the help of an optical telescope which is focused to the pupil of the eye to be examined. The crosshair of the telescope is centred to the pupil and all stimuli which are presented when the pupil is not in the middle of the crosshair are discarded. This monitoring of the fixation of the eye can be done visually by the examiner, which is rather unreliable and depends on the alertness of the examiner, or with electronic camera image processing system, or with automatic electronic video camera based eye-tracker, which requires complex and therefore expensive electronic systems and also requires prior calibration procedure.
The existing devices for examination of the visual field are usually large and technically complex, and therefore expensive, requiring a separate instrument table which occupies plenty of floor space in small examination rooms when not in use.
In some existing devices and methods for assessing ocular motor functions the orientation of the eye, i.e. where the line of sight (visual axis) or the fovea centralis of the retina of the eye is aimed at, or fixates, is monitored usually by automatic electronic video based eye-tracker, which requires complex and therefore expensive electronic systems. Before this kind of device can provide accurate information about the orientation of the eye, a calibration procedure must be conducted so that the device can match a detected specific position of the eye to eye's foveal fixation to known fixation target.